Patent GB-775589-A (GB)
Title: Improvements in or relating to short wave broadcast receiving aerials
Inventor: PLAISTOWE DONALD LEOPOLD
IPC: H01Q5/49
Filed: 1954-10-15
Abstract: 775,589. Aerials and aerial couplings. MARCONI'S WIRELESS TELEGRAPH GO., Ltd. July 20, 1955 [Oct. 15, 1954], No. 29728/54. Class 40(7) An aerial arrangement comprises an approximately rectangularly arranged conductor 1, 2 having two parallel longer sides and two parallel shorter sides. One of the shorter sides 2 may be attached to the longer sides by sliding couplings 3 and set screws so as to be adjustable laterally for tuning purposes. The shorter sides are preferably an eighth of the working wawelength long and the length from the midpoint of the longer side to the mid-point of the shorter side is made a quarter of the working wavelength. At least one of the shorter sides is provided with a bridged T matching section to which a feeder is attaced. The bridged T arrangement may consist of two co-linear rods 4 and 5 held by insulator 21 but electrically separated from each other. Bridge rods 8 and 9 having sliding couplings 6, 10 and 7, 11 on their ends connect the rods to the shorter side of conductor 1 and may be moved laterally to match the aerial to the balanced feeder 15 coupled to the inner ends of rods 4 and 5. This feeder is led through a hole in the side of conductor 1, which is tubular and inside it to a further hole inside insulator 13. Insulator 13 supports the aerial on quarter-wavelength support tube 12 but maintains it electrically insulated therefrom. The feeder 15 is led out through the tube 12 to the receiver and the tube itself may be bent to any convenient shape and provided with a support bracket 14. If desired a further bridged T matching arrangement may be associated with the second shorter side and a separate balanced feeder taken therefrom through conductors 1, 2 and tube 12 to another receiver (Fig. 2, not shown). If it is desired to obtain a single like polar diagram a reflector of tubing or wire as shown at 17, 18 may be suspended to one side of the aerial. The short side 18 of the reflector may be made adjustable in the same way as side 2 of the aerial for tuning purposes. Where the arrangement is mounted in a house loft the reflector may be held in place by cords 19. Where the longer sides of the aerial conductor are horiontal the aerial can be used for vertically polarized waves. If the longer sides are vertical and the bridged T connection on the upper shorter side (Fig. 3, not shown) horizontally polarized waves can be received. In an aerial of this type the matching bridge T arrangement (if any) on the lower horizontal shorter side of the aerial conductor may be arranged inside the loop and the insulator 13 and support and lead out tube 12 in the centre of the same side. In an arrangement for receiving horizontally polarized waves of one frequency, vertically polarized waves of twice that frequency and vertically polarized waves of a third unrelated frequency (Fig. 4) the cicumference of the loop is made a wavelength at the horizontally polarized wave frequency and the bridge T structure 4, 5 besides effecting matching at the first two frequencies also serves with the adjoining part of the aerial loop as a folded dipole resonant at the third frequency. A system of directors 22 may be provided to increase the signal pick up at the third frequency, the whole array for this frequency being, independently orientatable.. Where there is a second bridged T arrangement on the other shorter side of the loop this may form part of a similar array having a series of director elements. Specification 696,754 is referred to.